In texture processing in which a suitable roughness is given to the surface of a hard disk in a magnetic disk surface processing apparatus, the factors that affect the roughness include (1) processing pressure, (2) oscillation, (3) spindle rotation, (4) processing time, (5) rubber hardness, and (6) abrasive tape feed speed. Conventionally, these factors are each set to a fixed value initially, but trouble has been caused by discrepancies from the initial conditions due to such effects as changes in the temperature of the cooling fluid arising during processing, causing changes in the roughness of the disk surface, so that the prescribed roughness is no longer obtained.
What has conventionally been done to remedy such trouble is to measure the roughness of the disk surface every fixed number of processed disks, resetting the processing conditions once again as appropriate if the desired roughness is not attained. But this method leads to productivity problems, because the apparatus needs to be stopped while the roughness is measured and the appropriate processing conditions are reset.
For example, the time required to process a disk is given by the processing time-texture processing time+handling time; taking the processing time per disk to be 30 seconds and taking a batch to be 25 disks, the time needed to process one batch is 30 (seconds).times.25=12.5 (minutes). It takes about 8 minutes to take out one disk from every 25 disks and measure its roughness on both sides at four spots by a contact method. Resetting the processing conditions from this measurement data and then restarting the apparatus takes 2 minutes, so in these circumstances the down time comes to 10 minutes.
Assuming an operation time per day to be 8 hours, we have 25 (disks).times.60 (minutes).times.8 divided by (12.5(minutes)+10 (minutes))=533 disks, for a treatment quantity of 21.3 batches. The number of disks measured is 21, and since these are tested destructively, they are discarded, so the actual production comes to 533-21=512 disks per day.